1. Field of the Invention
This invention relates to a display apparatus, for example, a projection type display apparatus used to display a computer image or a video image on a large screen.
2. Related Background Art
In recent years, the use of display apparatus has been diversified in the field of image processing or the like and therefore, there have been required display apparatuses in which optimum color purity, color balance, illuminance, etc. are obtained in accordance with the use.
FIG. 24 of the accompanying drawings show the construction of a projection type display apparatus according to the prior art. In FIG. 24, white light emitted from a light source portion 1 passes through fly-eye lenses 3, 4, a PS conversion element 5, a condenser lens 6, etc., whereafter the light in the red band is transmitted through a dichroic mirror DM1 and the lights in the green to blue bands are reflected by the dichroic mirror DM1. Generally, as the light source, use is made of a halogen lamp, a metal halide lamp, a super-high pressure mercury lamp or the like, and as a color separating and combining optical element, use is made of a dichroic mirror, a dichroic prism or the like.
The red band light transmitted through the dichroic mirror DM1 exhibiting the spectral transmittance shown in FIG. 25A of the accompanying drawings has its optical path changed by 90xc2x0 by a total reflection mirror M1, and enters a liquid crystal display element 8R through a field lens 7R and a trimming filter TR exhibiting the spectral transmittance shown in FIG. 25C of the accompanying drawings, and is light-modulated there in conformity with an input signal. The light-modulated light enters a dichroic prism 9, and has its optical path changed by 90xc2x0 by the dichroic prism 9 and enters a projection lens 10.
On the other hand, the green-blue band light reflected by the dichroic mirror DM1 and having had its optical path by 90xc2x0 enters a dichroic mirror DM2 exhibiting the spectral transmittance shown in FIG. 25B of the accompanying drawings. From FIG. 25B, the dichroic mirror DM2 has the characteristic of reflecting the green band light and therefore, the green band light is reflected there and has its optical path changed by 90xc2x0, and enters a liquid crystal display element 8G through a field lens 7G and a trimming filter TG exhibiting the spectral transmittance shown in FIG. 25D of the accompanying drawings, and is light-modulated there in conformity with the input signal. The light-modulated green band light enters the dichroic prism 9 and the projection lens 10 in the named order.
The blue band light transmitted through the dichroic mirror DM2 enters a liquid crystal display element 8B through the intermediary of a condenser lens 11, relay lens 12, field lens 7B and total reflection mirrors M2 and M3, and is light-modulated there in conformity with the input signal. The light-modulated blue band light enters the dichroic prism 9, and has its optical path changed by 90xc2x0 by the dichroic prism 9 and enters the projection lens. In the prior-art projection type display apparatus constructed as described above, when the contrast of each liquid crystal display element is sufficiently high, the color purity of the red band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirror DM1 and the trimming filter TR, the color purity of the green band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirror DM1, DM2 and the trimming filter TG, and the color purity of the blue band light is determined by the spectral characteristic of the source light and the spectral transmittances of the dichroic mirrors DM1 and DM2.
As described above, in the construction of the prior-art projection type display apparatus, the design of each optical element has been made such that optimum color balance and color purity are obtained.
However, depending on the use of the projection type display apparatus, there are various requirements such as a case where bright display is required even if the apparatus becomes bulky, a case where bright display is required even if color purity is reduced, and a case where color purity is unnecessary in a black-and-white mode.
In the conventional projection type display apparatuses, in order to enhance color purity, a light having a wavelength of 570 nm-600 nm has been cut to thereby obtain optimum color balance and color purity, but in the case of many lamps, the peak exists in the vicinity of 580 nm in terms of spectral distribution. When a wavelength in the vicinity of this is used, it becomes possible to improve illuminance.
As such an example, mention may be made of a projection type display apparatus described in Japanese Patent Application Laid-Open No. 7-072450. In the description of this publication, there is proposed a projection type display apparatus having in an optical path optical elements differing in spectral characteristic, and provided with a mechanism for retractably inserting the optical elements. Thereby, display giving priority to brightness or display giving priority to color reproducibility can be realized by an apparatus, but when the optical elements are inserted to thereby effect the display giving priority to color reproducibility, the light in the entire wavelength range or the two-color wavelength range is transmitted through the optical elements, and since the optical elements are band cut filters, the transmittance of the wavelength necessary for projection is low, and this has led to the problem that the display becomes darker than necessary.
In order to solve this problem, Japanese Patent Application No. 1-235479 is mentioned as an example in which a moving third optical element is disposed at a place where only the red or green wavelength range is transmitted and an edge filter is used as the optical element, whereby the transmittance of the wavelength necessary for projection is high and the reduction in the quantity of light during the display giving priority to color reproducibility is made as small as possible, but in this case, there arises the problem that the brightness and color taste when priority is given to color reproducibility are changed by the unevenness of the cut wavelength in the manufacture of a dichroic mirror for dividing the light into the red band light and the green band light. At the same time, there has also arisen the problem that with the unevenness of the brightness of the display giving priority to color reproducibility, the up rate of brightness of the case where priority is given to brightness to the case where priority is given to color reproducibility becomes uneven.
Describing this in detail, assuming that the brightness of the lamp itself is not uneven, the absolute value of the brightness in the case of the display giving priority to brightness is constant because the spectral distribution of the lamp is intactly utilized. However, as regards the brightness when priority is given to color reproducibility, light of 570 nm-600 nm cut to enhance the color purity thereof is changed to e.g. 565 nm-600 nm or 575 nm-600 nm by the unevenness of the cut wavelength in the manufacture of the dichroic mirror and therefore, the brightness and color taste in the case of the display giving priority to color reproducibility become uneven. Along therewith, the up rate of brightness of the case where priority is given to brightness to the case where priority is given to color reproducibility becomes uneven.
Japanese Patent Application Laid-Open No. 7-318883 and Japanese Patent Application Laid-Open No. 9-211449 may be mentioned as examples in which the unevenness of brightness and color taste due to such unevenness of the cut wavelength in the production of the dichroic mirror is restrained by the use of a dichroic mirror subjected to inclination correction moving in a direction parallel to a direction in which the dichroic mirror is inclined with respect to an optical axis. In both of these publications, it is a feature that a dichroic mirror subjected to inclination correction is provided in a color combining system, and the dichroic mirror is moved in a direction parallel to the direction in which the dichroic mirror is inclined with respect to the optical axis to thereby approximate the cut wavelength for an on-axis ray to the design value and restrain the unevenness of brightness.
In Japanese Patent Application Laid-Open No. 9-211449, an inclination correction is made to a dichroic mirror for combining the red wavelength band and the green wavelength band, and provision is made of means for moving the dichroic mirror in a direction parallel to the direction in which the dichroic mirror is inclined with respect to the optical axis, and in this correction, to effect the adjustment of color reproducibility and the adjustment of the luminance of a screen, such a light utilizing method that for example, 585 nm or less is the green wavelength band and a wavelength longer than that is the red wavelength band is most efficient.
By doing so, the adjustment width is widened in such a manner that for example, the adjustment of the red wavelength range is possible up to 585 nm-615 nm, and this is very efficient. However, considering color purity, lights of 570 nm-600 nm are lights reducing the purity of green and red, and that wavelength band must be used and this is not preferable.
Also, in order to increase color purity, use can be made of a dichroic filter or the like for cutting the lights of 570 nm-600 nm in color combination, but this is a band cut filter, and this leads to the problem that the transmittance of the wavelength necessary for projection is low and the screen becomes darker than necessary.
As another method of increasing color purity, there is conceivable a method of installing a dichroic filter or the like for each color before effecting color combination, but according to this method, the adjustment width of color reproducibility and screen luminance becomes small, and this is not preferable.
Color purity can also be increased by a method of using lights of 570 nm-600 nm until it is color-combined with only one of the red wavelength range and the green wavelength range, and putting the light of that wavelength range out of the optical path by a dichroic mirror for effecting color combination, but according to this method, the adjustment of color reproducibility and screen luminance can be effected only in a single color, and this is not preferable.
Such an example is described in Japanese Patent Application Laid-Open No. 7-318883. According to this, an inclination correction is made to a dichroic mirror for combining the red wavelength band and the green wavelength band, and provision is made of means for moving the dichroic mirror in a direction parallel to a direction in which the dichroic mirror is inclined with respect to an optical axis. This dichroic mirror follows a correcting method which corrects only the red wavelength band which is transmitted light and does not affect the green wavelength band which is reflected light, and effects the color correction of the red wavelength band as an embodiment. In this case, color purity is increased, but the number of colors corrected is limited to one, and this is not preferable.
When as described above, the dichroic mirror subjected to inclination correction and movable in a direction parallel to the direction in which the dichroic mirror is inclined with respect to the optical axis is provided in a color combining system, if design is made such that both of red and green can be corrected, there results the problem that color purity is reduced. Also, if an attempt is made to increase color purity, there will arise the problems that the transmittance of the wavelength necessary for projection is low and the screen becomes darker than necessary and that the adjustment width of color reproducibility and screen luminance becomes small, and an attempt to solve these problems would lead to the problem that the number of colors corrected is limited to one.
So, the present invention has as its object to provide a display apparatus which can solve the above-noted problems.
To achieve the above object, the display apparatus of the present invention is a display apparatus comprising:
a color separating optical system for separating light from a light source into a plurality of lights differing in color (wavelength band) from one another; and
at least one display element for modulating the plurality of lights differing in color (wavelength band) from one another;
the color separating optical system including at least one color separating surface subjected to inclination correction, the color separating surface subjected to inclination correction being movable.
The color separating surface subjected to inclination correction refers to a color separating surface subjected to such correction as prevents a cut wavelength from being varied by the difference in the angle of incidence of the light onto the color separating surface.
In the above-described display apparatus, the color separating surface subjected to inclination correction is movable in a direction parallel to itself.
In the above-described display apparatus, the color separating optical system has a plurality of color separating surfaces (including a color separating surface not subjected to inclination correction).
In the above-described display apparatus, the plurality of lights differing in color from one another include at least red, green and blue lights.
In the above-described display apparatus, the color separating surface is a surface a dichroic mirror has.
In the above-described display apparatus, the display element has a light combining optical system for combining lights from a plurality of display elements disposed correspondingly to the plurality of lights differing in color from one another for modulating the plurality of lights.
In the above-described display apparatus, the light combining optical system has three or more prisms.
In the above-described display apparatus, the light combining optical system is constructed such that four prisms are cemented together by an adhesive agent and wavelength selection reflecting layers assume a substantially cruciate shape.
The above-described display apparatus has means for causing an image to be displayed in a plurality of different kinds of display forms by changing the color purity of at least one of the plurality of lights differing in color from one another.
In the above-described display apparatus, the means for causing an image to be displayed in a plurality of different kinds of display forms changes the color purity of the at least one light by putting an optical element into or out of the optical path of the at least one light color, or changing the posture of an optical element disposed in the optical path.
In the above-described display apparatus, the optical element is disposed between the color separating optical system and the display element.
In the above-described display apparatus, the optical element is an edge filter.
Also, to achieve the above object, the projection type display apparatus of the present invention is a projection type display apparatus comprising:
the above-described display apparatus; and
a projection optical system for projecting the light from the at least one display element.
Also, to achieve the above object, the projection type display apparatus of the present invention is a projection type display apparatus provided with:
a plurality of image display elements;
a color separating optical system for color-separating light from a light source into a plurality of color lights;
an irradiating optical system for irradiating the plurality of image display elements with the lights from the color separating optical system;
a color combining optical system for combining the lights from the plurality of image display elements; and
a projection optical system for projecting the lights combined by the color combining optical system onto a projection surface;
the projection type display apparatus having on the optical path of at least one of the plurality of color lights an optical element having the characteristic of transmitting therethrough a region of a predetermined wavelength or longer in a visible light region but blocking a region of wavelengths shorter than the predetermined wavelength, or a converse characteristic;
the color separating optical system having at least one color separating surface subjected to inclination correction, the color separating surface being movable.
In the above-described projection type display apparatus, the color separating surface subjected to inclination correction is movable in a direction parallel to itself.
In the above-described projection type display apparatus, the color separating optical system has a plurality of color separating surfaces (including a color separating surface not subjected to inclination correction).
In the above-described projection type display apparatus, the plurality of color lights include at least red, green and blue lights.
In the above-described projection type display apparatus, the color separating surface is a surface a dichroic mirror has.
In the above-described projection type display apparatus, the display elements are disposed correspondingly to respective ones of the plurality of color lights, and have a light combining optical system for combining the lights from a plurality of display elements for modulating the plurality of lights.
In the above-described projection type display apparatus, the light combining optical system has three or more prisms.
In the above-described projection type display apparatus, the light combining optical system is constructed such that four prisms are cemented together by an adhesive agent and wavelength selection reflecting layers assume a substantially cruciate shape.
The above-described projection type display apparatus has means for causing an image to be displayed in a plurality of different kinds of display forms by changing the color purity of at least one of the plurality of lights differing in color from one another.
In the above-described projection type display apparatus, the means for causing an image to be displayed in a plurality of different kinds of display forms changes the color purity of the at least one light by putting an optical element into or out of the optical path of the at least one light color, or changing the posture of an optical element disposed in the optical path.
In the above-described projection type display apparatus, the optical element is disposed between the color separating optical system and the display elements.
In the above-described projection type display apparatus, the optical element is an edge filter.
Also, to achieve the above object, the projection type display apparatus of the present invention is a projection type display apparatus comprising:
image display elements of three colors R, G and B;
a color separating optical system for color-separating light from a light source into the three colors R, G and B;
an irradiating optical system for guiding the color-resolving lights of the three colors R, G and B to the image display elements of the respective colors;
a color combining optical system for combining the lights from the plurality of image display elements; and
a projection optical system for projecting the lights combined by the color combining optical system onto a projection surface;
the projection type display apparatus having in the optical path of the R color light and/or the optical path of the G color light an edge filter retractably insertable into the optical path and having the characteristic of transmitting therethrough a region of a predetermined wavelength or longer in a visible light region but blocking a region of wavelengths shorter than the predetermined wavelength, or a converse characteristic;
the color separating optical system having two dichroic mirrors, one of the two dichroic mirrors which separates a light including the R color light and a light including the G color light from each other being subjected to inclination correction, the dichroic mirror subjected to inclination correction being movable in a direction parallel to a color separating surface the dichroic mirror has.